Tharsis · gate 22

Tharsis is a vast volcanic plateau centered near the equator in the western hemisphere of Mars. The region is home to the largest volcanoes in the Solar System, including the three enormous shield volcanoes Arsia Mons, Pavonis Mons, and Ascraeus Mons, which are collectively known as the Tharsis Montes. Current consensus is that Tharsis overlays a hot spot, similar to those thought to underlay volcanic island chains on Earth.

source · Wikipedia